* Prepare and bake brownie mix according to package directions for fudge-like brownies. Cool completely on a wire rack.

* Meanwhile, in a small bowl, cream the butter, confectioners' sugar and vanilla until light and fluffy. Place in a heavy-duty resealable plastic bag; cut a small hole in a corner of bag; set aside.

* Line a baking sheet with waxed paper. Dust with cocoa; set aside. Cut brownies into 15 rectangles. Using a 1-1/2-in. heart-shaped cookie cutter, cut out a heart from the center of each brownie. Reserve cutout centers for another use. Place brownies on prepared baking sheet. Pipe frosting into centers of brownies. Yield: 15 brownies.